1. Field of the Invention
This invention is concerned with a device and method for tissue engineering. More particularly this invention relates to a bioabsorbable device and a method for promoting controlled new tissue in-growth into voids or cavities occupied by the device as portions of the device are selectively absorbed within a host thereby minimizing collapse of surrounding, pre-existing host tissue into the engineered site. The device and method are particularly well suited for soft tissue engineering applications such as breast reconstruction and the healing of wound cavities.
2. Related Art
In the area of reconstructive surgery, tissue engineering is one approach to correct defects caused through removal of cancerous cells or debridement of other malignant masses of cells. Breast reconstruction is important for patients who undergo surgical procedures due to breast cancer. Some of the options for breast reconstruction include insertion of permanent implants (prostheses) and autologous tissue flap techniques using the latissimus dorsi as a flap, transverse rectus abdominis musculocutaneous flap, or free flap. Some of the prosthetic implants include anatomic saline implants and silicone bag-gel implants. However, disadvantages have been reported for these types of implants; for example, anatomic saline implants have been reported as having the disadvantage of persistent rippling and difficulty of the choice of size (Breast reconstruction by inflatable anatomical implant. Ann Chir Plast Esthet, 1999 June; 44(3): 239-45) and silicone bag-gel breast implants have been associated with leakage of silicone gel, which causes fibrous thickening, and various degrees of inflammation (“Bleeding” of Silicone from Bag-Gel Breast Implants, and its Clinical Relation to Fibrous Capsule Reaction. Plast Reconstr Surg, 1978 June; 61(6): 836-41). Even without the leakage of the silicone gel, this type of implant can cause periprosthetic capsules and excessive capsular sclerosis (Talc Deposition in Skin and Tissues Surrounding Silicone Gel-containing Prosthetic Devices, Arch Dematol, 1994 January; 130(1):48-53). Autologous tissue flaps have been reported potentially leading to necrosis (Breast Reconstruction: Autologous Tissue versus Implant, Zentralble Chir 1998; 123 Suppl 5:110-2).
U.S. Pat. No. 5,716,404 discloses methods and compositions for reconstruction or augmentation of breast tissue. Dissociated cells, preferably muscle cells, are implanted in combination with a suitable biodegradable, polymeric matrix to form new tissue. Two types of matrices are disclosed: a polymeric hydrogel formed of material such as an alginate having cells suspended therein, and a fibrous matrix having an interstitial spacing of between about 100 and 300 microns. In a preferred embodiment, the cell matrix is implanted in conjunction with tissue expander devices. As the cell-matrix is implanted, or cells proliferate and form new tissue, the expander size is decreased, until it can be removed and the desired reconstruction or augmentation is obtained.
The present invention provides an advance over the prior art by providing a fully bioabsorbable device capable of setting to the desired shape and being replaced by controlled in-growth of host tissue as hereinafter described.